This paper investigates the structural behavior of a new type of Composite Structural Insulated Panels (CSIPs) for load-bearing wall applications. The proposed composite panel is made of low cost orthotropic thermoplastic glass/polypropylene (glass-PP) laminate as a facesheet and Expanded Polystyrene Foam (EPS) as a core. The proposed CSIP wall is intended to overcome problems of the traditional Structural Insulated Panels (SIPs). These problems include termite attack, disintegration due to flood water, mold buildups and poor penetration resistance against wind borne debris. Full scale experimental testing for three CSIP panels was conducted to study the behavior of CSIP walls under eccentric load. Further, pull off strength tests were conducted to determine the bonding strength between the glass-PP facesheet and EPS foam core. Facesheet/core debonding was observed to be the general mode of failure. This study provides also analytical models to predict the interfacial tensile stress at the core/facesheet interface, critical wrinkling stress and deflections for a structural CSIP wall member. In addition, finite element modeling was also conducted using ANSYS software in order to model the response of CSIPs walls under in-plane loading. Experimental results were validated using the proposed analytical models and FE modeling, and were observed to be in good agreement. Furthermore, a parametric FE study was conducted to investigate the influence of key design parameters on the behavior of CSIPs. The study showed that span-to-depth ratio and core density have a significant effect on the structural performance of CSIP wall panels.